Robert McWhirter, an expert in constitutional and immigration law, is not aware of any past instance in which a local law enforcement official has faced federal charges for not complying with an ICE directive. And yet the DOJ is threatening prosecutions. 

Bolts
“A Chilling Effect”: A New York County Faces Federal Threats for Not Complying with ICE - Bolts
The Tompkins County sheriff released a man who’d served his sentence. Now the Trump administration, eager to force local officials to collaborate...